commit 94ebc36420e05bf4b83ede037c851f75d5d50ca2
author Tomáš Pecka <tomas.pecka@cesnet.cz> Wed Jan 24 16:46:39 2024 +0100
committer Tomáš Pecka <tomas.pecka@cesnet.cz> Thu Jan 25 22:16:49 2024 +0100
tree b54bc76773f1ea436346593605f9a40668ffa5f1
parent 26ac0faacbbf0890930db28c28a81e334728d26e

health: read systemd unit state from ListUnits call

When we are registering units after listing all units, we did query
their state explicitly using another DBus call. This is, however, not
required, because ListUnits() method returns both the ActiveState,
and the SubState of the unit [1].

[1] https://www.freedesktop.org/wiki/Software/systemd/dbus/#Manager-ListUnits

Change-Id: I5fb6a1d214833c98675e8ab9c92d427c926fd321

src/health/SystemdUnits.cpp

diff --git a/src/health/SystemdUnits.cpp b/src/health/SystemdUnits.cpp
index fea93c8..275df08 100644
--- a/src/health/SystemdUnits.cpp
+++ b/src/health/SystemdUnits.cpp
@@ -35,13 +35,17 @@
 
     // Register to a signal introducing new unit
     m_proxyManager->uponSignal("UnitNew").onInterface(managerIface).call([&](const std::string& unitName, const sdbus::ObjectPath& unitObjectPath) {
-        registerSystemdUnit(connection, unitName, unitObjectPath);
+        registerSystemdUnit(connection, unitName, unitObjectPath, std::nullopt);
     });
     m_proxyManager->finishRegistration();
 
     /* Track all current units. Method ListUnits() -> a(ssssssouso) returns a DBus struct type with information
      * about the unit (see https://www.freedesktop.org/wiki/Software/systemd/dbus/#Manager-ListUnits).
-     * In our code we need only the first (index 0, the unit name) field and seventh (index 6, unit object path) field.
+     * In our code we need the fields:
+     *  - 0: the unit name
+     *  - 6: unit object path
+     *  - 3: unit activeState
+     *  - 4: unit subState
      */
     std::vector<sdbus::Struct<std::string, std::string, std::string, std::string, std::string, std::string, sdbus::ObjectPath, uint32_t, std::string, sdbus::ObjectPath>> units;
     m_proxyManager->callMethod("ListUnits").onInterface(managerIface).storeResultsTo(units);
@@ -49,7 +53,7 @@
         const auto& unitName = unit.get<0>();
         const auto& unitObjectPath = unit.get<6>();
 
-        registerSystemdUnit(connection, unitName, unitObjectPath);
+        registerSystemdUnit(connection, unitName, unitObjectPath, UnitState{unit.get<3>(), unit.get<4>()});
     }
 }
 
@@ -60,7 +64,7 @@
 }
 
 /** @brief Registers a systemd unit by its unit name and unit dbus objectpath. */
-void SystemdUnits::registerSystemdUnit(sdbus::IConnection& connection, const std::string& unitName, const sdbus::ObjectPath& unitObjectPath)
+void SystemdUnits::registerSystemdUnit(sdbus::IConnection& connection, const std::string& unitName, const sdbus::ObjectPath& unitObjectPath, const std::optional<UnitState>& unitState)
 {
     sdbus::IProxy* proxyUnit;
 
@@ -92,10 +96,15 @@
     proxyUnit->finishRegistration();
     m_log->trace("Registered systemd unit watcher for '{}'", unitName);
 
-    // Query the current state of this unit
-    std::string newActiveState = proxyUnit->getProperty("ActiveState").onInterface(m_unitIface);
-    std::string newSubState = proxyUnit->getProperty("SubState").onInterface(m_unitIface);
-    onUnitStateChange(unitName, UnitState{std::move(newActiveState), std::move(newSubState)});
+    // Query the current state of this unit if not provided
+    if (!unitState) {
+        std::string newActiveState = proxyUnit->getProperty("ActiveState").onInterface(m_unitIface);
+        std::string newSubState = proxyUnit->getProperty("SubState").onInterface(m_unitIface);
+        onUnitStateChange(unitName, UnitState{std::move(newActiveState), std::move(newSubState)});
+    } else {
+        onUnitStateChange(unitName, *unitState);
+    }
+
 }
 
 /** @brief Callback for unit state change */